Spatial and seasonal fluctuations of Ichthyoplankton assemblage in the Mediterranean coast of Morocco (Southwestern Alboran Sea)

Ichthyoplankton represent the first life stages of fish. The study of ichthyoplankton is crucial to understanding marine ecosystems and plays an important role in the management and durability of fisheries resources. During March and October of 2019, two oceanographic ichthyoplankton surveys were conducted in the Mediterranean Sea of Morocco from Tanger to Saadia by studying the horizontal structure of the ichthyoplankton species assemblage and its relation to environmental parameters. The average surface water temperature was (15.8°C in spring and 16.4°C in autumn). The fish eggs and larvae were more abundant in March than in October (21268 eggs/10m² and 14084 larvae/10m² in spring and 10094 eggs/10m² and 13796 larvae/10m²). In both seasons, fish eggs from the families Sternoptychidae and Sparidae were dominant (10101 eggs/10m² and 7527 eggs/10m² in spring and 4422 eggs/10m² and 3928 eggs/10m² in fall, respectively). However, Myctophidae larvae were the most abundant in the study area, reaching 7601 larvae/10m² in spring and 11021 larvae/10m² in autumn. The environmental parameters: temperature, salinity and chlorophyll-a (surface) seem to directly influence the spatial distribution of ichtyoplancton. On the other hand, it seems that predation by jellyfish (Pelagia noctiluca)was a very important factor that added to the factors that influenced the distribution of the species of fish eggs and larvae. This work represents the first survey conducted in the southwestern Alboran Sea, which studies the horizontal structure of the ichthyoplankton species assemblage and its relation to environmental factors in the spring and autumn of 2019.